Organic light-emitting diode (OLED) displays, also known as organic electro-luminescent displays, are a new type of flat panel display. Because of its advantages such as simple manufacturing process, low cost, low power consumption, high luminance, wide range of operating temperature, light in weight and thin in volume, fast response, easy color display and large screen sizes, easy compatibility with drivers of integrated circuits, and easiness in forming flexible displays, OLED displays have a promising future of wide applications. Presently, light-emitting devices are used to develop flexible OLED display panels, which use flexible base plates to replace conventional glass base plates for flexibility of panels.
Flexible OLED display panels are a new development trend for the display panels. Because next generation of flexible OLED display panel uses polyimide (PI) as flexible base plate, the PI base plate has to have excellent properties, and number of defects in PI base plate has to be low in order to increase manufacturing yield of flexible OLED display panels. It is also required to reduce damages to PI base plates during manufacturing process of OLED display panels.
However, during the manufacturing process of OLED display panels, excimer laser annealing and excimer laser stripping of glass substrates results in certain degree of damage to PI base plates, even making PI base plates to form holes.
To reduce damage to PI base plates caused by the excimer laser during the manufacturing process of display panels, a buffer layer is generally formed. In such a buffer layer, SiNx prevents Al/Ba/Na ions from diffusing into PI base plates to decrease current leakage, and because SiOx has superior thermal insulation, dissipation of heat during crystallization of a-Si decreases and larger grain sizes can be formed. In addition, SiNx has good ability to isolate ions and causes lower stress when in contact with glass, and SiOx has better wetting angle with respect to polysilicon boundary. Thus, a stack of SiNx/SiOx is generally adopted. However, in the base plates of flexible OLED display panels, SiNx layer does not directly contact glass substrate, thus SiNx layer is functioned for insulation and buffer only. Thermal insulation ability of SiOx during excimer laser annealing (ELA) is still insufficient, and PI layer is easily to be damaged.
Therefore, the buffer layer of flexible base plate in conventional OLED display panels does not have remarkable effects in protecting PI layer, leading to not only easily causing damage to PI layer but further influencing quality of OLED display panels.